Has Your Sunscreen Stopped Working? 3 Signs It’s Time to Buy a New Formula

Sunscreen is the ultimate getaway insurance, promising a guilt-free, burn-proof romp on the beach or day by the pool. But your application is futile if the formula in question has stopped working. In fact, there are a number of elements that may inhibit the power of your lotion, cream, or spray to protect your skin from UV rays. Luckily, they’re as easily identifiable as they are entirely preventable.

“It all starts with what’s inside the bottle,” says cosmetic chemist Ni’Kita Wilson. “You want the product you’re using to be as fresh as the day you bought it.” Often ignored, a simple guide to the product’s effectiveness is the expiration date provided by the manufacturer, printed right on the bottle. “Sunscreen’s efficacy is tested to up to three years,” says dermatologist Elizabeth Quigley. “Anything that’s past its expiration date belongs in the trash.”

Even if you are technically within that crucial window, poor storage can cause early expiration. For example, placing a bottle on a windowsill can force the sunscreen to absorb UV rays between uses, weakening its potency when it is applied to your body. Exposure to heat can also compromise the stability of a formula, causing it to separate. “If you squeeze the bottle and [a runny] liquid comes out first, toss it. It’s important that the sunscreen is applied uniformly and there are no uncovered gaps on the skin,” says Wilson.

Of course, if you’re using the FDA-recommended dosage, a bottle of sunscreen should almost never last long enough for any of the aforementioned issues to occur. “Two ounces every two hours,” says Quigley, who adds that no matter how high the SPF, sweating, swimming, and friction caused by movement or toweling off can lead to accidental exposure, making reapplication essential. “You shouldn’t have anything left after a full day in the sun.”